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Topic Review (Newest First)
01-23-2013 11:12 PM
cdminter59
Chasing a ghost in a 350 SBC.

Before going thru the expense of changing intakes try swapping the thermostat to a 195* to see if it helps. I was wondering since GM spun off Delphi and Delphi not making plugs anymore what kind of plugs do you use? AC-Delco 41-110, NGK Irddium TR5IX, NGK V-Power TR5 gap .040
01-23-2013 04:31 PM
steeny Yep, and if the intake/carb heat passage is blocked off in combo with a cold plug they will misfire. Had friends little 283 that he ran without an airfilter (don't ask!!) on actually iced up the throttle on cold, moist winter days and would misfire.
01-23-2013 04:03 PM
Hacksaw I don't know if it mattered or not, but it is a late model roller Vortec block with one piece pan and rear main. Those engines use a 195 degree thermo I believe. But due to the carb intake I figured thermostat shouldn't matter? Would the combo of thermostat and spark plug heat have any affect?
01-23-2013 04:00 PM
Hacksaw When it's cold, it runs between 170-180 degrees. When it's warmer it's running around 190. There is a 180 thermo installed. It does seem like it runs much better around the 190 range
01-23-2013 03:51 PM
steeny Beginning to sound like poor fuel atomization in the intake and ports leading to a lean misfire. Does this engine ever get to operating temp when it is cool outside?
01-23-2013 03:47 PM
Hacksaw Drove the car again today to work. 32 degrees this morning. Ran decent but the slight hesitation was back at part throttle. Now it's 60 degrees and the car is running awesome. Seriously thinking the RPM Air Gap isn't for cold weather! I hate to buy a RPM Vortec intake just to try. But I don't know of any to borrow. My heads are the Edelbrock E-Tech 170 so...
01-22-2013 07:28 PM
cdminter59
Chasing a ghost in a 350 SBC.

Yeah, I think that pump might be suspect too. Probably losing volume as rpms increase. Try your electric pump maybe it will be the fix. Hope it works for you.
01-22-2013 05:53 PM
Hacksaw
Quote:
Originally Posted by abritton77 View Post
I was using a summit racing summit racing 110 gph mechanical pump. I had installed it over the winter along with some other changes is why it took me so long to figure it out. I would swear that our description sounds just like my nightmare. It cost me a small fortune to figure it out.
This Holley Big End pump was purchased off eBay. I'm sure its a knock off just like the summet pumps are
01-22-2013 05:20 PM
abritton77 I was using a summit racing summit racing 110 gph mechanical pump. I had installed it over the winter along with some other changes is why it took me so long to figure it out. I would swear that our description sounds just like my nightmare. It cost me a small fortune to figure it out.
01-22-2013 07:59 AM
cdminter59
Chasing a ghost in a 350 SBC.

I read in one of your post about the trash you found in the 4150 carb. What type fuel filters are you using? Most manufacturers recommend a 100 micron filter at the tank. Also a 40 micron filter in the line up front. Another interesting thing I read the other day is not to use teflon tape on any gas or oil fittings. It said to use a paste type sealer with teflon in it. I used Permatex 59235 when rebuilding my engine last year. You have replaced everything in the ignition system and it hasn't fixed the problem yet. How about your fuel. Gas with 10% ethanol has a shelf life of about 3 months. The ethanol absorbs water from the atmosphere. I have heard of using a timing light to watch the gas as the carb squirts the gas. IDK but it is said you can see water in the gas. Here is the article (advertisement) i was reading. USA Fuel
01-22-2013 05:50 AM
cobalt327
Quote:
Originally Posted by Hacksaw View Post
Then started playing with pump arm gap. Adjusted to have a slight gap in the pump arm and pump lever.
Just to be sure- the gap is only at WOT, not at rest (idle), right?

Quote:
Still a bit concerned with having 24 degrees initial, but there is zero pinging.
I'm guessing the cam is fairly 'healthy'. If that's the case, absolutely nothing wrong or unusual about the amount of initial timing.

BTW, good job on the carb tuning as well as the timing. A LOT of guys stumble (npi) on this.
01-22-2013 05:40 AM
Hacksaw
Quote:
Originally Posted by abritton77 View Post
Sounds just like the gremlin that I had last year. I thought it was ignition related and I upgraded everything with no luck. I would think at times it was fixed but then it would prove me wrong. I switched to an electric fuel pump and the problem was gone for good.
Now the fuel pump has not been changed at all. It is a new Holley Big End 110 gph mechanical pump. I Have always used an electric pump until now. And I've been thinking of switching back to electric!
01-22-2013 05:38 AM
Hacksaw
Quote:
Originally Posted by steeny View Post
This might sound out of line but I had a tach some years ago do what you are describing. It was intermittent miss fire at times then other times a miss that was consistent around 3k then disappear. I unhooked that tach and the problem went away for good. Just a thought.
Hahahaha. Yeah, already tried unhooking the tach. No change.
01-21-2013 09:38 PM
steeny This might sound out of line but I had a tach some years ago do what you are describing. It was intermittent miss fire at times then other times a miss that was consistent around 3k then disappear. I unhooked that tach and the problem went away for good. Just a thought.
01-21-2013 07:30 PM
abritton77 Sounds just like the gremlin that I had last year. I thought it was ignition related and I upgraded everything with no luck. I would think at times it was fixed but then it would prove me wrong. I switched to an electric fuel pump and the problem was gone for good.
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